As one of the countries currently having this War on Drugs, I'd say simply jailing user, peddlers and manufacturers is not enough. Having read Freakonomics and also seen it in real life, dealers are pretty much disposable. There are always new idiots to fill the slots. Manufacturers as well. Get rid of some and the others simply get more business. Get rid of them all and someone would still show up to play in the now even more lucrative field.

Supply expands to fulfill demand. The key is to prevent people from starting using these drugs anyway. Rehabilitation would also work but is definitely more expensive and time-consuming than prevention.

I'm ambivalent about drug legalization. On one hand I understand the practicalities. Legal manufacturers can be regulated and so the quality of their products would be better, hopefully reducing deaths. These manufacturers are also taxable and so the gov't also earn money. The question is what drugs should be made legal. Another is the tendency of certain drugs to increase resistance, requiring the use higher doses or more potent drugs.

I'm not sure about recreational marijuana but I heard that this don't cause as much violence as meth. Hopefully people also don't build resistance to it.